Hitachi wh 14daf2 Technical Data And Service Manual page 12

7-2-2. Bolt tightening torque characteristics
Figure 5 shows relationships between time and tightening torque for individual bolt types and sizes. While the
data are useful for handy reference, actual tightening torque will vary depending on tightening conditions and
other variables. For details, please refer to Para. 8-3, Tightening Torque Variation.
NOTE: The term "tightening time" indicates the impact time after the lower surface of the bolt has come
in contact with the material into which it is being tightened.
In the tightening conditions shown in Fig. 5, the screws are being tightened directly into a steel
plate; accordingly, the torque goes up very abruptly in comparison with ordinary bolt tightening
conditions.
Washer
Bolt
Washer
Nut
Model WH 14DAF2
* The following bolts were utilized:
Ordinary bolt; strength grade 4.8
High-strength bolt; strength grade 12.9
.
N m
.
(kgf cm)
Ordinary bolt
120
(1200)
100
(1000)
80 M12 (t = 25 mm)
(800)
60
(600)
M10 (t = 10 mm)
40
(400)
M8 (t = 10 mm)
20
(200)
0
1
0 2
Tightening time: sec
.
N m
.
(kgf cm)
High-strength bolt
120
(1200)
M12 (t = 25 mm)
100
(1000)
80
(800)
60
M10 (t = 10 mm)
(600)
M8 (t = 10 mm)
40
(400)
20
(200)
0
1
3 0
Tightening time: sec
Fig. 5
--- 9 ---
Strength grade is read as follows:
4.8
Yield point or durable force:
(45,500 psi)
Tensile strength of the bolt:
(56,900 psi)
2 3